Mission critical has a broad definition that is most commonly defined by facility owners as a function of their perceived importance of continuous operation of their facility. Common examples of mission critical facilities include data centers, control rooms, emergency call centers, and military facilities. Essentially, a mission critical facility is one where continued operation is of tantamount importance to the business owner or operator.
When thinking of the needs of a mission critical facility, the concern of a fire rendering the facility inoperable is often at the top of a facility owner’s or operator’s list of risks. Furthermore, when considering how to mitigate a fire in one of these facilities, one must consider the speed of cleanup to return the facility to operational status as soon as possible. This is where clean agents come into play.
Design standards for clean agents
When thinking about clean agents, at first, most industry professionals will often reference NFPA 2001: Standard on Clean Agent Fire Extinguishing Systems. The 2015 edition of NFPA 2001 is the most recent edition, and the standard’s scope is stated as follows: “This standard contains minimum requirements for total flooding and local-application clean agent fire-suppression systems. It does not cover fire-extinguishing systems that use carbon dioxide or water as the primary extinguishing media, which are addressed by other NFPA documents.” The standard identifies the system components, system design considerations, local application requirements, and inspection, testing, maintenance, and training provisions. NFPA 2001 defines a clean agent as an “electrically nonconducting, volatile, or gaseous fire extinguishant that does not leave a residue upon evaporation.” Typically, a clean agent fire-extinguishing system installed in compliance with NFPA 2001 can be installed in a normally occupied space, as these systems are designed to extinguish a fire without reducing the oxygen levels within a space to below safe limits for humans.
Another standard to consider when discussing clean agent systems is NFPA 12: Standard on Carbon Dioxide Extinguishing Systems. The current 2015 edition of NFPA 12 addresses design and installation for total flooding and local application for carbon dioxide fire-extinguishing systems. It is crucial to note that there are significant restrictions for using carbon dioxide fire-extinguishing systems in normally occupied spaces due to the hazardous low-oxygen environment created by the system discharge.
The benefit of clean agent extinguishants is that they do not cause additional damage to the facility beyond what was caused by the fire. Typically, protected spaces would be ventilated to remove any gaseous remnants of the discharge, and once individual pieces of equipment are repaired, the facility can return to business as usual very quickly.
Building code considerations
NFPA 2001 and NFPA 12 are standards that require adoption by a particular code, jurisdiction, or owner. For example, the model building codes incorporate references to NFPA 2001 and NFPA 12, wherein compliance with the model building code requires conformance to the relevant standard for the selected system. The two most common model building codes incorporate NFPA 2001 as follows:
NFPA 5000: Building Construction and Safety Code, 2015 edition, references both NFPA 12 and NFPA 2001 in sections 126.96.36.199.7, 188.8.131.52, and 184.108.40.206.3 as approved approaches for providing automatic fire suppression in power-generation structures of Type I or Type II construction that are used to house generators, turbines, and flue gas-treatment equipment. The use of these systems within power-generation structures is permitted as the primary means of fire suppression in lieu of an automatic fire sprinkler system, allows for extended egress travel distances, and enables unlimited building height and area.
NFPA 5000 Section 55.5.1 also generally references both NFPA 12 and NFPA 2001 as the applicable standards for the design, installation, and maintenance of carbon dioxide and clean agent fire-extinguishing systems, respectively, for use in any occupancy or building type.
IBC and IFC
The 2015 editions of the International Building Code (IBC) and International Fire Code (IFC) contain limited references to clean agent and carbon dioxide fire-extinguishing systems. Sections 904.8 and 904.10 in both model documents provide references to NFPA 12 and NFPA 2001 for carbon dioxide and clean agent systems, respectively. Therefore, compliance with the NFPA standards is incorporated within the model code requirements. Furthermore, compliance with the manufacturers-listing requirements is mandatory. IBC Section 904 provides the requirements for alternative automatic fire-extinguishing systems, which are generally used to protect specific hazards within a building as opposed to serving as the primary fire protection system for a building. With regard to IBC/IFC compliance, the use of a clean agent or carbon dioxide system as a replacement for a required automatic fire sprinkler system will require approval from the local authority having jurisdiction (AHJ). Additionally, IFC Section 901.6.1 requires that carbon dioxide and clean agent systems be inspected, tested, and maintained in accordance with the appropriate NFPA standards.
In the absence of incorporation into a model building code, or the locally amended and adopted version of a model building code, an individual AHJ or facility owner may require compliance with NFPA 2001. It is always important to verify all codes and standards applicable to a project at the beginning, to ensure that the design complies with the appropriate regulations.
Extinguishing system agents and options
The U.S. Environmental Protection Agency’s (EPA) Significant New Alternatives Policy (SNAP) provides an evolving list of fire suppression and explosion-protection agents that have been assessed by the EPA for overall risk to the environment and human health in the following categories:
The SNAP list includes options for both total flooding agents and streaming agents. NFPA 2001 defines a total flooding system as “… consisting of an agent supply and distribution network designed to achieve a total flooding condition in a hazard volume,” while a streaming agent is addressed as a locally applicable system “… consisting of a supply of extinguishing agent arranged to discharge directly on the burning material.” NFPA 12 provides similar, but not exact, definitions.
With carbon dioxide systems, the agent is always the same, but manufacturers offer systems in a variety of storage configurations, sizes, and pressures. In most instances, these types of systems are used for industrial applications with low occupant loads that can be evacuated prior to discharge or spaces that are not normally occupied.
The remainder of clean agent systems is subdivided into two primary categories: halocarbon agents and inert gas agents.